


Day 6: Soul Magic

by WatermelonTuesdays



Series: Sheith Monster Fuckers 2019 [6]
Category: Voltron: Legendary Defender
Genre: Alternate Universe - Fantasy, Alternate Universe - Magic, Anal Fingering, Anal Sex, Bisexual Shiro (Voltron), Blood, Bottom Shiro (Voltron), Demon Keith (Voltron), Dom/sub, Explicit Consent, M/M, Master/Slave, Orgasm Delay/Denial, Rimming, Role Reversal, Spit As Lube, Top Keith (Voltron), Violence
Language: English
Status: Completed
Published: 2019-10-06
Updated: 2019-10-06
Packaged: 2020-11-25 18:23:04
Rating: Explicit
Warnings: Graphic Depictions Of Violence
Chapters: 1
Words: 4,342
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/20916527
Author URL: https://archiveofourown.org/users/WatermelonTuesdays/pseuds/WatermelonTuesdays
Summary: Keith has been soul-bound to his king, Shiro, for years, magically forced to obey his every command. But when Shiro finally gets the bright idea to command a little more from Keith, he finds Keith has other plans in mind.





	Day 6: Soul Magic

**Author's Note:**

> Keith is kind of a demon in this... I didn't make it super clear what the galra are. You can easily see this as a mashup of the 2 prompts again, soul magic and oni, but I kind of just avoided specifics because this one took several attempts to write.

The galran soldier screams an unholy noise as Shiro’s cleaver rends it into two separate pieces. Purple skin and dark blood go flying, and Shiro only has time to spit out a mouthful of foul blood before he’s spinning and splitting another beast in half. 

It’s a sea of purple and red.

The monsters fell upon Shiro’s party as they returned home through the mountainous path that connects Shiro’s kingdom with Allura’s. Two of Shiro’s party died instantly, the rest fought valiantly but they were hopelessly overwhelmed. 

Shiro is the only human left standing, and he batters his way through wave after wave of purple onslaught. 

Once upon a time he had been captured by galran demons, and he was experimented on with their strange magic, but no more. Now, Shiro is stronger than ever; the whole horde of galran armies can rain down on him and he will never falter.

Neither will Shiro’s secret weapon. 

There’s another cry of agony as Shiro’s cleaver messily brains a galra soldier, but it’s nothing compared to the cacophony of pain coming from Shiro’s left. For, though Shiro may be the only human left, he is neither alone nor defenseless. 

“Keith!” Shiro shouts, “to me!” He can’t be heard over the death screams playing like an orchestra on his left, but he can feel through the bond of ancient magics that Keith knows he’s been summoned.

The sounds of indiscriminate slaughter grow louder until Shiro can see the carnage from the corner of his eye. 

With a sound kick to one of the horde’s chest, Shiro sends a beast flying into Keith’s wake. Moments later he sees the shredded remains of the galra splatter the tree boughs around them. Shiro laughs as he lops another’s head clear off, and he can hear it echo in a manic sound of psychotic joy from Keith.

The half-galra stands at least 2 feet shorter than the full-blooded monsters that surround them, but what he lacks in height and muscle he makes up in ferocity. The human and galran magics mix in the young creature to make him one of the most powerful monsters Shiro has encountered. On a good day, Keith looks more human than anything else, but on a day like this his evil heritage is made plain. His skin is a pale, shining purple that imitates the deep hues of the horde. His eyes burn with a yellow rage, and his teeth and claws sharpen to razors.

In his bloodlust, Keith moves more like an animal, on all fours. Human and galran magics flow from him indiscriminately, pouring off him in waves that Shiro will feel in his bones long after the fight.

“Watch my 6,” Shiro commands. He can feel Keith’s hesitance to follow the order, but the young beast has no choice. He bends, the way he always bends, and follows his master’s order.

Keith moves to Shiro’s back and protects his master ferociously. Shiro hacks his way through the masses of galran soldiers while Keith shreds and tears any who come within his grasp. They make their way through to the heart of the horde, until they are completely surrounded. 

The long, wide grins of the galra around them are malicious as they close ranks tight around them. They lick their lips in anticipation, thinking they are finally going to taste the lifeblood of the Garrison king. But Shiro has no plans to die today. 

“Fire,” he commands, and lifts his blackened, cursed hand.

“No!” Keith protests, his voice wild and deep from his berserk state. Using magic to end a fight like this is cheating in Keith’s eyes. He is resentful of each galran he does not have the pleasure of personally dismembering.

Though Keith protests, his magic is already building at Shiro’s bidding. Shiro can feel the heat of the fire building at his palm. He can feel the surge of galran magics coursing from Keith and funneling through Shiro’s hand.

Keith screams.

The fire bursts forth with a heat that the galra cannot withstand. It burns their grins in place and leaves their jaws set in grotesque, smoldering smiles. 

Keith’s magic floods through Shiro, using him as both vessel and conduit. Though it is Keith’s power, Shiro gives it direction. Shiro is the only one who can direct it. That is the pact between the two since they first met over a decade ago, when Keith was still scrawny, hungry, and terrified.

Shiro had stumbled upon the young creature shortly after his escape as the galran champion. He was trekking through the galran waste pits on the edge of their territory far to the west when he found the small, feral, half-breed. He was thin, wild, and half-starved. It was nothing for Shiro to pin him and recite the ancient spells, invoking the deep magics and binding the boy’s soul to his own. 

The magic took his right hand, leaving him with a blackened claw able to channel Keith’s unrivaled powers. It also left him with the most loyal slave to ever exist. Magically unable to deny his master’s wishes, Keith has followed Shiro to the ends of the Earth and brought whole kingdoms to heel. Keith is at once the Garrison kingdom’s most feared citizen and also its foremost protector. 

Keith’s power is unrivalled. The high Shiro feels, knowing he commands such power, and feeling the strength of Keith’s magic flowing from his fingertips, is indescribable. It’s stronger than the bloodlust of battle. It’s more addictive than any drug his sorcerers can concoct. It’s more pleasurable than any man or woman Shiro’s ever lain with.

Shiro raises his hand and the flames burst outward in a rolling typhoon, burning the horde whole, save for a few stragglers.

The fire dies the moment Shiro closes his fist. 

Those remaining flee. Keith watches them with a whimpering noise, not unlike a dog held back from the hunt. Though Shiro’s blood is pumping with adrenaline, he surveys Keith coolly. His lips quirk at the edges with something akin to fondness. Nothing can quench the beast’s thirst for blood. 

“Alright, chase them down. But be quick about it.” 

~*~*~*~*~*~*~

Half an hour later, Keith finds Shiro at the edge of a stream, rinsing his blood-spattered furs in the cool water. Though the battle is long over, the thrill of the fight and the rush of magic still sings through Shiro’s blood. He feels elated. 

His entire body feels as though it has been filled with bubbles. Every movement of his body reminds him of the surge of power he felt before. Colours look brighter, the breeze smells sweeter, and everything feels better in the aftermath of the high.

It’s always like this after he uses Keith’s magic in battle. It can last hours if he uses a strong enough spell, and the fire he conjured was definitely strong enough for this to last half a day, at least. So, Shiro allows himself to sink into the feeling and revel in it.

He hums to himself as he works the bloodstains out of his clothes. The sky is bright blue and marked with light clouds that attracts Shiro’s attention. The feel of the fur in his hands is sublime; it’s so soft even when wet, and it feels luxurious to his over-stimulated brain.

There’s only one thing that would make this high even better. Lazily, Shiro contemplates his options. He could step into the cool waters, let the changing temperature spike his arousal, and reach a hand into his pants and take himself apart slowly. Or he could step back, strip naked in the sunshine and bake the pleasure into his every limb.

Either way would be a luxury he’s never afforded himself before. Always, at the end of the battle he’s surrounded by his wounded comrades and pressing kingly matters that spoil his high and bring him back to reality far too quickly. But today, he is alone, and free to indulge himself as he likes.

A derisive click of a tongue reminds Shiro that he is not, in fact, alone. Keith stands several feet away, waded hip-deep into the cold water, and washing himself with scoopfuls of water. It’s a beguiling sight, even as the beast glares at Shiro with golden eyes. The fabric of his shirt clings to pale purple skin and the water catches the light like falling diamonds as it drops back down to the stream. 

Shiro doesn’t often get to see Keith like this, still purple from their fight. When Keith fights, he draws more on his galra heritage, and he returns to a more human colour palette as he calms down. The colour fades with Shiro’s high, and like the high, it’s always gone by the time Shiro has a moment to himself to think. 

Not that Shiro minds; he usually prefers Keith to look human. But at the moment, there’s something tantalizing and intriguing about galra Keith.

“Keith. Come here,” Shiro commands. The order comes from the same part of his brain that’s still debating the various ways Shiro could get himself off, and Shiro feels his heart begin to race as he realizes the situation. 

Keith is his to control.

“Why?” comes the sharp reply. Keith straightens up, his shirt open enough that more pale purple skin catches the sunlight. His skin looks soft and supple like this, betraying the hard lines set by strong muscles. It looks _good_.

Keith’s eyebrows furrow and he scowls as he steps towards Shiro. He knows he can’t fight Shiro’s orders, but he loves to question them.

“Want to see what a real man looks like?” Keith teases, his voice hard and cutting. He steps over-close, coming into Shiro’s personal bubble, trying to intimidate.

Shiro knows this is a power move for Keith, trying to make Shiro uncomfortable with his proximity, and drawing attention to his galra heritage. He always takes any chance he can get to fight back within the confines of his orders: moving too slow or taking things too far just to piss Shiro off. 

As always, the best way to fight Keith’s impertinence is by not reacting, so Shiro doesn’t argue, and he doesn’t step back.

His eyes rake over Keith’s exposed chest. This isn’t exactly the first time Shiro’s noticed how good-looking Keith is, but it is the first time the thought is followed by a distinctive swooping feeling, low in Shiro’s gut.

Everything feels so good in his post-battle high – it’s better than good food and better than good sex – and it’s about to get even better. 

If that purple tone to Keith’s skin is any indication, he’s still riding a high of adrenaline as well. 

“Show me, then,” Shiro says. He reaches out and tugs Keith’s shirt so it opens just a little more, exposing black chest hair and a dark purple nipple. 

Keith’s eyebrows raise and he grins maliciously as his hands rise to follow Shiro’s order. “What’s this? Is his highness finally tired of the pureblood humans and ready to go slumming with a dirty half-breed?” He slowly pulls his shirt apart and stretches his body before tossing the garment to the ground. He steps closer, his eyes dark. For a moment, Shiro wants to back down, but he resists the urge. 

He’s in control; he’s been in complete control of Keith for over a decade. This is just another way he’s in control. 

“Kiss me.” 

A thrill runs through Shiro at the command. He’s ordered Keith around so much over the years, he sometimes forgets the immense power that connects them, but now he feels it sharp as day. It’s like a white light connecting them, forcing Keith to Shiro’s will. 

There’s precious little resistance on Keith’s end as he closes the distance between them. 

Shiro expects Keith to give him a soft, little, fleeting kiss. Something that will fulfil the command without indulging any of the intent behind it. As such, he is completely unprepared when Keith snakes a hand behind Shiro’s neck, holding him in place before crushing their lips together in a powerful and hungry embrace. Keith’s lips move against Shiro’s with purpose, easily prying Shiro’s open to slip in a warm tongue. 

The kiss keeps going and going until Shiro is hazy. It overpowers him, and he feels himself clinging desperately to Keith. They go stumbling backwards until Shiro is pressed bodily against a tree, and still Keith doesn’t relent. 

Sharp claws close around Shiro’s neck while more grip at his thigh, trying to lift Shiro more firmly against Keith. Shiro obliges, and locks his leg around Keith’s waist, desperate for more, for anything Keith will give him. 

He feels lost to Keith’s mercy. But that’s not right. It should be Keith lost to Shiro’s mercy. 

It takes a moment for Shiro to find the strength to push Keith away, and when he does, they are both winded and warm from their embrace. Keith’s cheeks look a darker shade of purple than Shiro’s ever seen, and he knows his own face must been similarly flushed. 

Already, Shiro misses the warm strength of Keith’s body against him, but he’s hesitant to order another kiss. He needs to keep control of the situation. 

But the moment Shiro’s arms drop from Keith’s chest, the half-galra surges back into Shiro’s space. His hands slide between Shiro’s royal furs to touch at the thin material draping Shiro’s sides. His mouth closes in on Shiro’s ear, where he speaks in a low, seductive whisper.

“What’s the matter, Shiro? Am I too much for you?”

Shiro groans. He’s pushed back against the tree, and Keith’s knee squeezes between his legs, pinning him in place. The sensation skitters along Shiro’s skin like a wildfire spreading through the forest.

“I’m more man than any of those twittering idiots you line your bed with back at the castle.” Keith lowers his head and drags sharp teeth along the column of Shiro’s throat. “Can’t you handle me?”

Fuck! Shiro can feel his resolve slipping. Keith moves his body against Shiro’s and Shiro can’t help but ride it like a wave. He needs to regain control now, or else he knows he’ll be lost to Keith’s designs. 

But the magic is still there. The magic that binds them together. It can’t ever be undone. It’s Shiro’s only tool.

“P-pleasure me,” Shiro orders, his voice shaking with desire.

He hears Keith’s teeth clack together in a grin. Keith pulls back so Shiro can see the wild delight burning in his eyes, and the wide stretch of his evil grin. “My pleasure.” He says it with such glee that Shiro feels himself gulp nervously. 

“Let’s get you out of your clothes, my lord,” Keith says in a mocking tone. He trails his fingers and claws over Shiro’s body as he slowly removes Shiro’s furs and shirt. It’s a light and teasing touch that builds Shiro’s anticipation more than anything. 

This is closer to what Shiro was expecting. Though Keith’s tone is sarcastic, his actions are submissive, and Shiro breathes a sigh of relief. He closes his eyes and lets himself bask in the soft touch and gentle bite of Keith’s claws. 

“You look so handsome, my lord,” Keith adds. Then he licks a strip up Shiro’s bare chest, stopping to suck a nipple into his mouth while his fingers unlace Shiro’s pants. “And how excited.” Keith palms at Shiro’s hard cock, pressing it into Shiro’s stomach and grinding against it with the heel of his hand. 

It feels fucking amazing! Everything does. And as Keith stoops to guide Shiro’s pants down over his feet, Shiro opens his eyes again just so that he can take in the image of his purple demon on his knees before him. Shiro can’t help the look of pride at getting Keith to act so subservient for him, and he digs his fingers into Keith’s long, dark hair just to feel him down there. Finally in his place.

Keith busies himself with stripping Shiro bare, then he puts both hands to Shiro’s hips and gives Shiro’s cock a good look over. Again, the anticipation rolls through Shiro. He’s so ready to be pleased. His hard cock is only inches from Keith’s mouth, and he’s sure Keith is going to devour it. It’s going to feel so good, Shiro can barely contain himself, and he gives Keith’s hair a little tug to urge him on. 

Then Keith meets Shiro’s eyes, and the look in those golden eyes is anything but subservient. “So excited…” Keith says again. He looks more like someone who’s just won a battle, rather than someone about to suck his master’s cock. “… for a half-breed like me.” Keith lifts one of Shiro’s legs and places it over his shoulder, then he lifts the other and does the same so that Shiro is sitting on Keith’s shoulders, his back pressed against the tree, his fingers still buried in Keith’s hair. “You’re a slut, aren’t you, my liege?” Keith asks, sincerely.

The insult cuts through Shiro. But as he opens his mouth to protest, Keith spreads Shiro’s ass cheeks with sure fingers and he dives, mouth-first, at Shiro’s asshole. 

All thought of protest flies instantly from Shiro’s mind. 

This is _not_ what he wanted, and not what he was expecting, but it feels so amazing, Shiro forgets to complain. Keith’s tongue is wicked against him. It’s hot and wet, and it opens Shiro up like an expert. No one’s ever touched Shiro like this before; as much as he’d like to say he resisted, within moments he finds himself rocking against Keith’s face trying to bury that tongue deeper within himself. 

The scratch of the tree bark against Shiro’s back is all that keeps him grounded from Keith’s onslaught. He’s aware of little else besides the sure, sinful movements of that tongue. When Keith starts to add fingers to the mix (long, thin ones that reach deep inside and find pleasures Shiro’s never felt before in his life) Shiro doesn’t even hear himself start to speak.

“God, that’s good, that’s so good Keith. Right there! That’s it! Fuck! _Fuck_! Right there. It’s so good. It’s So. Fucking. Good, Keith.” Shiro’s eyes are closed tight from the pleasure. His whole body is on fire with it. His hands shake with their grip on Keith’s hair, and his hips move of their own volition. His cock drips precum on himself and on Keith. “I’m close, I’m close,” he starts to chant as he feels the pressure grow overwhelming. 

He’s so close. It’s right there. He can feel it.

And then Keith pulls away and drops Shiro suddenly back on his feet.

The drop off from his expected orgasm is jarring and it throws Shiro into a rage. “No!” he growls, grabbing at the tree behind him to keep himself steady. “I said to pleasure me!”

“And I will,” Keith answers calmly, getting to his feet and brushing the dirt off his knees. He licks his lips as he unlaces his pants and pulls out a hard, throbbing, purple penis. 

“What the fuck do you think you’re doing with that?” Shiro asks, still angry, though unable to look away from the beautiful, thick curve of cock in Keith’s hand. 

“Pleasuring you,” Keith answers easily. He reaches out and grabs Shiro by the hip, spinning him around with galran strength and wrapping one arm around Shiro’s waist to hold him in place.

“No, you’re not!” Shiro protests. 

Keith leans so that Shiro has no choice but to bend in half. It doesn’t matter that Shiro is bigger because Keith is still stronger. His fingers find Shiro’s hole and circle it teasingly before plunging in, deep as before. “Yes I am. You said to pleasure you, and this is how I’m going to pleasure you.”

Any further protest from Shiro is lost to the keening noise he makes as Keith’s fingers light up his insides once more. 

“See? Now be a good king and take it for me.” Keith removes his fingers and replaces them with the tip of his cock, swirling and teasing over Shiro’s entrance. “I’ve got something nice and thick here. Perfect for a slut like you, kingy.”

Keith keeps teasing at Shiro’s rim, but he doesn’t thrust in, just holds himself there, rubbing, waiting. The hand securing Shiro in place moves along Shiro’s chest to tease at a nipple, and he drags his sharp teeth along Shiro’s back. It’s a show of power, and Shiro knows it. Just like he knows Keith is waiting for Shiro’s consent before slipping inside him. 

He’s not doing it out of chivalry. Keith wants to make Shiro admit to his desires. He wants Shiro to relinquish control and let Keith take the reins. 

And though Shiro is loathe to admit it, he does love this. He even loves the name calling.

He feels powerless and dirty, but in the best way imaginable. 

“Fuck me,” Shiro orders.

“With pleasure,” Keith replies into the curve of Shiro’s back.

He eases into Shiro bit by bit, tormenting Shiro with his slowness. It’s a tight squeeze, and eased only by Keith’s spit, but it fills Shiro with a burning desire he already finds addictive. 

“You’re taking me so well, Shiro. Such a good little slut,” Keith praises as he bottoms out. “Look at you, bent over and taking your little pet’s cock like a champion. What would the courtiers say if they saw you like this, hmm?” Keith eases his way back out and then slides much more urgently back into Shiro, knocking the breath out of him. “Fucking your little half-breed demon pet?” 

Shiro moans at the thought. He knows they’d be horrified, and right now the idea of their disgust makes it all feel that much sweeter. 

“H-harder,” Shiro pants. The pleasure is building quickly now, and he wants to meet it head on.

“Oh? I can give you harder, Shiro.” Keith pushes Shiro down further, so that Shiro has to put his hands to the ground to keep from falling face-first into the grass. Shark claws dip into Shiro’s hip as Keith changes his grip to fuck harder and faster into Shiro. He lifts one of Shiro’s legs up off the ground, giving himself better access, and he pounds Shiro, hard and mean. “Like this? Hmm? Is this how you want it, sire? This how you want me to fuck you?”

“Yessss,” Shiro gasps. Keith is hitting him dead-on and he feels his orgasm building, faster and stronger than before. “Right there. Don’t stop.”

“Oh, I’m not fucking stopping, Shiro. Don’t you worry.” 

Keith keeps pounding Shiro, hard and fast. Shiro is lost to the pleasure. He can’t think, he can hardly breathe. All he knows is that each slap of Keith’s thighs against him brings a spark of bliss unlike anything he’s ever felt before, and he never wants it to end. 

His body tenses as his orgasm approaches a second time, and Shiro needs it to happen. He needs to come! He orders Keith again not to stop, fearing how the demon will use his newfound power. 

He’s right there. He’s so close this time, he can taste it. 

And then Keith’s hand drops from Shiro’s chest and closes around his cock, gripping tight at the base and staving off Shiro’s orgasm for a second time.

“_NO!_” Shiro cries. “God _fucking_ dammit, Keith!” 

“I’m not stopping,” Keith argues. He doesn’t stop. He fucks Shiro as hard and fast as ever. His grip over Shiro’s cock doesn’t loosen either, and Shiro’s trapped between immense pleasure and an ever-building release. 

It’s overwhelming. It brings tears to Shiro’s eyes.

“Please. Please, Keith,” he begs.

“Yes, Shiro. Beg for it,” Keith urges. He brings them down to their knees and pushes Shiro’s head down into the grass, changing the angle of his assault so that the pleasure becomes near unbearable. 

“Please, Keith. Please let me come. I’ll do anything. Please, please, please!” Shiro whimpers into the grass, his words shaking and heaving around each gasping breath that Keith fucks out of him. Shiro’s too far gone now to realize begging isn’t a command, he can’t understand how he has the power end this quickly with a simple order. All he knows is that his release is, quite literally, in Keith’s hands, and he’ll do anything to see it through.

Keith’s thrusts start to stutter, his set pace faltering and growing wildly off rhythm as Keith nears his own release. 

It all happens at once, then. Shiro feels the explosion of Keith inside him just as Keith’s teeth sink into the meat of Shiro’s shoulder. At the same moment, Keith loosens his grip and rubs Shiro’s cock in a tight fist. 

Shiro’s orgasm crashes through him like a lightning bolt. It’s so violent, he loses his sight for several moments. Still Keith fucks into him, churning out more pleasure with every thrust until Shiro is a twitching mess beneath him. 

Still he keeps going and going until they are both groaning. 

“Shiro. Shiro, tell me to stop,” Keith says around clenched teeth as the whole ordeal starts to tip towards painful.

“Stop.”

Keith pulls out with a sigh of relief and drops to the ground at Shiro’s side. 

In a haze, Shiro opens his eyes and watches in astonishment as Keith’s skin turns from purple, to mottled pink, to pink in a matter of seconds. He looks completely human now, though he’s just as attractive as ever.

“Hey,” Shiro says, grabbing Keith’s attention. Keith’s blue human eyes flutter open and settle on Shiro. “Don’t ever tell anyone about this,” Shiro orders quietly. (He has a reputation to uphold and a kingdom to rule.) He waits until he feels the order sink in through their bond. “Good. Now, kiss me again.”

Hesitantly, Keith shuffles over and presses a slow kiss to Shiro’s lips. This time, Shiro doesn’t fight to try and take control, he lets Keith lead the kiss. Shiro’s learned what’s good for him.

**Author's Note:**

> Thanks for reading! 
> 
> I really like this prompt and feel like it's a proper Horny™ idea, but I'm not sure if the soul magic is present enough? I don't know, it's hard to have Shiro commanding Keith around like that and not have it be very dub-con-y. Plus, I really like the idea of Keith undermining all of Shiro's commands and domming him despite the fact that he's forced, magically, to be submissive. 
> 
> Also, I realized tonight that all my previous fics in this event (except, I think, the first one) I forgot to tag tops and bottoms. I know that can be a bit of a big thing for some people, but I'm honestly too lazy to go add all the tags, so I'll just say that it's going to be a mixed bag. I'm trying to keep it from being too heavy on one or the other being the monster and on one or the other being bottom. 
> 
> Also, tomorrow's prompt is a 'free day' and I know that means it's up to me, but I honestly kind of took it as a break day. Maybe once this month is over/all the rest of the prompts are completed (whichever one comes first) I'll go in and fill in the free days... There's a couple of ones that I wouldn't mind writing sequels to.....
> 
> You guys have been amazing with the comments and kudos! I really love it! It's a huge help. There's a chance my life is about to become WAY busier than expected and my prompts won't all get done on the day-of, but my current plan is that if I fall behind, then in November I'll keep this going and fill in the rest. I'm enjoying myself too much right now not to.
> 
> As always, you can follow me on twitter or tumblr for fic updates.  
Twitter: [@WTuesdays](https://twitter.com/WTuesdays)  
Tumblr: [WatermelonTuesdays](https://watermelontuesdays.tumblr.com/)


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